UK passage: 42 birds
Family: Reed warblers
Aquatic warblers have brown upperparts with black and buff streaks, a white or buff throat, and white or buff underparts with fine brown streaks on the breast and flanks. They have a rounded tail which is brown with black streaks above and buff underneath.
On the head the nape is brown, the forehead is yellow, buff, or brown and the crown is dark brown with a white central stripe. They have dark brown eyes with a prominent white supercilium, the bill is blackish-brown with a pink base on the lower mandible, and the legs and feet are pink. Male and female aquatic warblers are similar.
Juveniles resemble the adults but lack the streaks on the breast and flanks.
Aquatic warblers breed from early May to late July. Females build the nests from grass, plant stems, leaves, and cobwebs lined with finer materials concealed in dense vegetation over marshy ground or water.
Aquatic warblers lay 4-6 eggs which are brown and spotted with yellowish-grey. They are incubated by the female alone for 12-15 days and chicks fledge after 13-14 days.
They may sometimes produce 2 clutches in a breeding season.
Aquatic warblers eat mostly insects, caterpillars and spiders tending to stay hidden on the ground when searching for food.
In the UK aquatic warblers are best seen at the end of August. They are found in the coastal reedbeds on the south coast in Devon and Cornwall.
The aquatic warbler is the only globally threatened passerine bird in mainland Europe.